The present inventions relate generally to the manufacture of heat exchangers formed from plastic tubing. More particularly, heat exchanger fabrication production lines and methods for producing plastic tubing based heat exchangers are described.
Heat exchangers come in a wide variety of configurations and are used in a wide variety of applications. One type of simple heat exchanger contemplate simply running a plurality of riser tubes 21 between a pair of header pipes 23 (often called manifolds) as illustrated in FIG. 1. The header pipes 23 and risers 21 can be formed from a wide variety of materials, but one class of heat exchangers utilizes simple extruded plastic tubing. A variety of plastics may be used to form the panels, although generally a dark, thermoplastic material is used. The illustrated type of heat exchangers have a number of desirable attributes including that they are simple, lightweight, and relatively rugged when exposed to adverse environmental conditions including repeated freezing and thawing, exposure to water and/or corrosive chemicals and prolonged exposure to the sun. They are also relatively simple to produce. Thus, they can be used in a wide variety of systems. By way of example, for a number of years, the assignee of the present application has produced and sold this type of heat exchanger for use in solar heating applications and thermal energy storage systems.
A number of existing patents describe techniques for producing plastic heat exchangers. By way of example, U.S. Pat. Nos. 3,934,323 and 4,243,454 describe suitable techniques. Although the existing production techniques work well, there are continuing efforts to improve the efficiency of the production process.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, improved plastic heat exchanger production systems are described. In one method aspect, plastic tubing is extruded, cut to tube segments of desired length and conveyed onto a platform. A plurality of clip strips are fed across the platform and the tube segments are sequentially automatically inserted into the clip strips. The clip strips are then cut at desired lengths to provide heat exchanger tubing panels of a desired size or sizes. In a preferred system, header pipes are then attached to the respective ends of the cut heat exchanger tubing panels.
In some implementations either flat tubing panels or panels having laterally offset tubes may be produced using the same production line. In one embodiment, heat exchanger panels having laterally offset tubes may be created by cutting one or more middle clip strips into spacer segments and rotating the spacer segments to laterally offset at least some of the tubes.
In another aspect of the invention, a heat exchanger production line is described. The production line includes an extruder for extruding plastic tubing and a tubing cutter for cutting extruded plastic tubing into tube segments and a plurality of aligned tube inserters. The tube inserters are each arranged to receive the extruded plastic tubing and an associated clip strip and to automatically inserting the tubing into their associated clip strip. Clip strip cutters are provided for cutting the clip strips at desired locations to provide heat exchanger tubing panels. In a preferred embodiment, a pipe attacher is provided to attach header pipes to the ends of the heat exchanger tubing panels.
In some embodiments a plurality of clip strip feeder reels are provided, with each feeder reel being arranged to feed an associated tube inserter. In various embodiments, a support beam is provided to carry the tube inserters. In this arrangement, the tube inserters may be slidably mounted on the support beam to facilitate adjusting the spacing of the clip strips in the heat exchanger tubing panels. A rotator may also be provided to rotate spacer segments cut from a selected clip strip relative to other (typically end) clip strips to provide lateral spacing for some of the tubes in the heat exchanger tubing panel.
In one preferred arrangement, the extruder, a cooling trough, the tubing cutter and the tube inserters are arranged along one line and the clip strip feed reels, the clip strip cutters and the pipe attacher are aligned along a second line that transversely intersects the first line at the tube inserters.
In another aspect of the invention, improved tube inserters suitable for inserting plastic tubing into a plastic clip strip are described. In one preferred arrangement, the tube inserter includes a clip strip feed channel for receiving a clip strip and a tubing feed channel for receiving tubing. A clip strip advancer, an actuator and a clip strip cutter. The clip strip advancer is arranged to advance the clip strip through the clip strip feed channel. The actuator presses received tubing into the clip strip and the clip strip cutter is arranged to cut the clip strips when desired. In a preferred arrangement, a plurality of these tube inserters are slidably mounted on a support beam to facilitate the production of heat exchanger tubing panels.